Solvent recovery to reduce hazardous waste

Problem: Many pharmaceutical and nutraceutical products that are created from natural sources involve using solvent extraction to remove the desired components from the biomass. After extraction, the remaining wet cake material is considered a waste stream and is typically classified as a hazardous material due to the residual solvent content. In order to reduce the cost impact of these waste streams, manufacturers need a way to separate the residual solvent from the biomass material. A solvent recovery process could create both a recoverable solvent stream and a disposable, or potentially useable, biomass.

One example of this commercial requirement was:

  • Wetcake Biomass Rate: 300 kg/hr
  • Solvent Content: > 40%wt

Additional considerations included:

  • Maximum solvent content in dried biomass waste, per local waste regulations.
  • Biomass was intended to be re-purposed as animal feed and thus could not exceed 95°C.
  • Thermal processing systems needed to recover the solvent to be recycled back into upstream extraction processes.
  • Material coming from filter press was in large chunks and needed to be conditioned for material handling and efficient solvent removal.

Solution: The Solidaire® paddle dryer system by Bepex International was used as the heart of a complete solvent recovery system to remove the solvent from the biomass material. A Bepex Disintegrator was used to take the large pieces of wetcake from the filter press and break it down into coarse grind prior to the solvent recovery step.

At Bepex’s Process Development Center, wet cake was first broken down into smaller pieces in the Disintegrator. This created a coarse powder to help with material handling and solvent recovery. The material was then fed at a constant rate into the Solidaire, and the exhaust gas generated went through a condenser to recover the solvent. Because of the Solidaire’s efficiency and low residence time, cooking of the biomass was minimized, thus preserving it for potential animal feed use.

Benefits and Results:

Wetcake ValuesFinal Product
Solvent Content> 40%<500 ppm
Product ConsistencyLarge Pieces (2-3 inches)Flowable Powder
  • Reduced solvent content to safe levels below both disposable waste and animal feed regulations.
  • Solvent recycling allowed for the recovered solvent to be recycled back into upstream extraction operations.
  • Material temperature was controlled to maintain characteristics for animal feed.